What Causes the Uterine Lining to Thicken?

The thickening of the uterine lining or endometrium is a natural occurrence related to menstruation and pregnancy. It can also be triggered by conditions, such as endometriosis, endometrial hyperplasia and uterine fibroids, that need medical attention, according to Everyday Health.

Throughout the menstrual cycle, the ovaries secrete varying levels of estrogen to prepare the uterus for pregnancy. Upon ovulation or release of the egg, another hormone is secreted, the progesterone, which makes the endometrium even thicker. Without fertilization, the levels of these two hormones will decline, triggering the sloughing off of the lining. The process is accompanied by bleeding, making it thinner and marking the start of a new menstrual cycle, states Everyday Health.

High levels of estrogen coupled with very low amounts of progesterone leads to excessive growth of cells on the uterine lining, according to Healthgrades. Endometrial hyperplasia can also occur as result of taking estrogen hormones without taking progesterone, which causes an imbalance of the two hormones. This can lead to cancer as well.

Risk factors for uterine line thickening include polycystic ovarian syndrome, a disorder that affects the levels of hormones in women; obesity; diabetes; and menopause, reports Healthgrades. Tracking menstrual periods, keeping diabetes under control and losing weight if overweight help to reduce the chances of endometrial hyperplasia. Taking birth control pills and, with the help of doctor, undertaking hormone replacement therapy may help as well.

Signs and symptoms include missed menstrual periods, acne, heavy bleeding during menstruation and bleeding between periods, notes Healthgrades. Other symptoms include hot flashes, tenderness of the vagina, dry vagina and mood swings. Rapid pulse, extreme abdominal pain, loss of consciousness and fainting require immediate medical attention.